In present microelectronics technology, data storage is non-volatile (spin-based), whereas data processing is volatile (charge-based). Recently, attempts have been made to create architectures which are completely non-volatile. Spintronics, an alternative to microelectronics, represents one such attempt. The aim of spintronics-based devices is to store and process data solely in ferromagnetic materials, and to make the device completely non-volatile so as to increase its speed while reducing power consumption.
Many attempts have been made towards the realization of spin-logic or magnetic logic. For example, Imre et al. (2006, Science 311, p. 205) demonstrated magnetic logic based on a network of magnetostatically coupled magnetic elements, a scheme called magnetic cellular automata. The magnetostatically coupled ferromagnetic islands perform the logic operations by summing up the stray fields at the nodal dots which have different threshold switching fields. The main disadvantage of this device is that the magnetostatic coupling is weak compared to the demagnetizing fields. A small change in the structure during the fabrication results in completely different results.
Magnetic tunnel junction (MTJ) based logic devices have previously been proposed (for example, see R. Richter et al. (2002) Solid State Electron. 46, 639). The high current density required for the operation of these devices is their main disadvantage.
Alternative magnetic logic architectures are based on propagation of domain walls (DW) through a network of nanowires under the influence of a rotating external magnetic field—see D. Allwood et al. (2005) Science 309, 1688, the entire contents of which are hereby incorporated by reference. Allwood et al. fabricated four different structures in order to perform specific logic functions (AND, NOT, cross-over and fan-out).